1. Field of the Invention
This invention relates to an apparatus for applying glass beads to a surface. More particularly, this invention relates to a sensor for a glass bead application system which monitors the application of glass beads to a road.
2. Description of the Prior Art
The use of glass beads in marking a surface is well known as can be seen in U.S. Pat. Nos. 2,821,890; 3,057,273; 3,286,605; and 4,856,931.
U.S. Pat. No. 2,821,890 to Wilson teaches marking a road or highway surface with a coating material having small particles intimately mixed therewith. The small particles are made of a reflective material, for example, glass spheres, that have an auto-collimating that is effective in outlining traffic lanes during the evening when headlights or overhead lights reflect from the striping. However, this patent does not provide any means for monitoring the supply of reflective material. Hence, it is possible that the device could run out of the reflective particles, but marking of the roadway would continue as the person utilizing the equipment may not be aware that the flow of reflective material has ceased.
U.S Pat. No. 3,057,273, also to Wilson, suffers from the same deficiency as the device described above. That is, without means to monitor the supply of reflective material, it is quite possible that the roadway could be marked with a paint having no reflective particles combined therewith. This deficiency is particularly evident where the reflectivity of the marker is produced immediately upon application with a spray gun that ejects glass spheres onto the painted marker. These spheres are larger in size than those which are admixed to the paint itself. Where the topical application of reflective particles ceases, markings are produced which are not reflective until highly worn to thus expose the smaller particles premixed with the paint.
Wilson et al., U.S. Pat. No. 3,286,605, teaches an apparatus and a method for marking the surface of a road. This patent suffers from the same problem as the two Wilson patents discussed above. That is, there is no way of monitoring the stream produced by spray gun, and it possible that the supply of glass particles will cease, unnoticed, resulting in only paint being applied to the roadway.
Even further, U.S. Pat. No. 4,856,931 to Bollag teaches a device that lays a marking line. The line is first sprayed on the surface by spray gun. The painted is has reflective beads mixed therein. Subsequent to the painting of the line, reflective beads are applied with the beads adhering to the painted line. However, no device or method is suggested for monitoring the supply or flow of the reflective beads.